The invention is based on a semiconductor fuse for electrical consumers, in particular for electrical consumers in a vehicle electrical systems.
Electrical consumers, for example electrical consumers in a vehicle electrical system, must be protected from overload by means of suitable fuses or fuse circuits. Fuses of this kind are designed, for example, as electronic fuses and include semiconductor switches, which react when there is an overvoltage or overcurrent. In consumers that must be constantly supplied with voltage and which also need constant fuse protection, a fuse is required, which needs only a minimal static current. For example, in order to fuse protect an electrical control unit of a motor vehicle, which unit represents an electrical consumer, a fuse is required, which constantly protects the control unit even at times when the vehicle is not operating and the entire energy supply must come from the vehicle battery. For a fuse of this kind, it is necessary that it only require a small amount of static current. It would be even better if it did not require any static voltage at all and thus no load would be placed on the vehicle battery even when the vehicle is parked for long periods of time.
It is known to supply control units in motor vehicles with the battery voltage via semiconductor switches, where these semiconductor switches not only perform the function of supplying voltage, but also provide a certain protection from overcurrent and overvoltage. A vehicle electrical system in which the control unit is supplied with voltage from the vehicle battery via a semiconductor switch has been disclosed by DE-OS 196 45 944. In this vehicle electrical system, the electrical system control unit is electrically connected to the battery with the aid of a field effect transistor. If the field effect transistor is in a conductive state, the control unit is supplied with voltage. If the field effect transistor is switched into the non-conductive state, the control unit goes into a xe2x80x9csleep modexe2x80x9d in which it only receives a very small amount of current and after a renewed triggering of the field effect transistor, can be quickly supplied with voltage again and thus switched on.
The semiconductor fuse for electrical consumers according to the invention has the advantage that the consumers to be protected, for example control units in a vehicle electrical systems, are actually protected in a practically static current-free manner in which the consumers are advantageously connected and protected by means of semiconductor switches. The advantage of semiconductor fuses in comparison to conventional fuses is that a semiconductor fuse does not have to be replaced after being tripped, but is ready for operation again right away. In addition, a semiconductor fuse offers the advantage of individual adaptation of the reaction characteristic curve. Furthermore, it is easily diagnosable and requires only a low mechanical cost. The advantages of the invention are achieved by virtue of the fact that the actual semiconductor fuse is connected in parallel with a static current-free bypass with an integrated wakeup circuit. Altogether, this produces a static current-free semiconductor fuse.